This invention relates to an improved process of purifying a vinylically unsaturated compound prepared from the palladium-complex catalyzed reaction of an olefin containing a vinylic hydrogen and an aryl, allyl, vinyl, or benzyl halide. Specifically, the invention relates to an improved method of removing palladium and halide from the vinylically unsaturated compound.
The palladium-complex catalyzed vinylation of organic halides is described by Heck in U.S. Pat. No. 3,922,299 and in Organic Reactions, vol. 27, p. 345 (1982), both incorporated herein by reference. The reaction is represented by the following equation: ##STR1## wherein R is aryl, allyl, vinyl, or benzyl, the Pd-complex is typically palladium bound to a trivalent organophosphorous or organoarsenic moiety, and an organic or halo moiety. Heck teaches that the reaction can be carried out with or without a solvent, with suggested solvents being acetonitrile, tetrahydrofuran, methanol, dimethylformamide (DMF), and N-methyl-pyrrolidinone.
In U. S. Pat. No. 5,264,646, incorporated herein by reference, DeVries et al. discloses an improved process for the Heck-type vinylation reaction, wherein the reaction is carried out in a water-containing medium.
The crude vinylically unsaturated compound prepared by the methods described by Heck and DeVries et al. is advantageously purified to remove inorganics, particularly palladium and halide, from the crude product. This purification is particularly crucial, for example, for high performance electronic applications, where it is often necessary to reduce inorganic impurity concentrations to low ppm levels. Present purification processes, such as distillation, crystallization, or chromatography, are necessary, yet often insufficient for reducing these inorganic impurities to the desired levels. Indeed, multiple purification steps may be required to achieve the desired reduction of impurities. Furthermore, these processes do not provide an easy means for recovering and recycling palladium.
Because the recovery and recyclability of palladium is desirable, and multiple purification steps are undesirable, it would be an advantage to provide a simple means of reducing halide and palladium impurities in the crude vinylically unsaturated compound prior to a further purification step.